Pressure actuated switch



May 27, 1947 w. R. PETERSON 2,421,284

PRESSURE ACTUATED SWITCH Filed June 24. 1944 2 sheets4sheet 1 MaY 27,1947- v w. R. PETERSON 2,421,284V

PRES SURE ACTUATED SWITCH l l Filed June 24, 1944 2 Sheets-Sheet 2Patented May 27, 1947` A PRESSURE ACTUTED SWITCH. William B.. Peterson,Lowell, Ind., asslgnor to Vapor Car Heating Company, Inc., Chicago,

Ill., a corporation oi' New York Application June 24, 1944, Serial No.541,963

Claims.

This invention relates to certain new and usel'ul improvements in apressure actuated switch adapted to open 'or to close an electriccircuit in response to predetermined changes in tem- Derature.

The invention is directed principally to improvements in theconstruction of the several parts which simplify the assembly of thecombination structure as a whole.

One of the principal aims oi the present invention is to provide atemperature responsive switch of the above character in which the partsmay be conveniently assembled so that the switch may be normallymaintained either in its closed or opened positions so as to meet therequirements of the particular circuit in which the switch is used.

Another and more specic object is to provide a temperature actuatedswitch including a switch assembly and a temperature responsive motorfor actuating the switch, both of which are enclosed in a housing ofnovel construction. In this connection the invention includes theprovision of a sectional housing, in which the switch assembly and themotor assembly are mounted in separate compartments with capacity forquick and convenient disconnection of said assemblies for purposes ofinspection or repair. l

A further object is to provide a temperature actuated switch including aswitch member and a bellows motor for actuating the same, and

means associated with the bellows motor and adapted to be heated at alocation remote therefrom to generate pressure for actuating thebellows. One means herein shown for accomplishing this object includesthe provision of a tube containing a thermal sensitive fluid and adaptedto extend into a heat zone, whereby the expansion of the thermal iiuidin the tube results in operating the bellows motor. In anotherembodiment the fluid is contained wholly within an expansionchamber ofthe motor and the heat is transmitted to a wall o1' said chamber by ametallic heat conductor.

The invention is illustrated in certain specific embodiments in theaccompanying drawings wherein:

Fig. 1 is a vertical sectional view taken through l a pressure actuatedswitch constructed in accordance with this invention.

Fig. 2 is a fragmentary view of the structure shown in Fig. 1, thevsection being taken on line 2--2 of Fig. 1 and looking in the directionof the arrows.

Fig. 3 is a plan view of the structure shown in Figs. 1 and 2.

Figs. i and 5 are views similar to Figs. 1 and2 but showing the switchassembly in a position inverted relative to the position shown in Figs.1 and 2.

(Cl. 20o-83) Fig. 6 is a sectional view through a modified form ofswitch which is particularly suitable for use in situations of thecharacter illustrated.

The embodiment of the invention illustrated in 5 Figs. 1 to 3, inclusivemay be described brielly as comprising a sectional housing I Il, aswitch assembly II, and a bellows motor I2. The said housing includes anupper section I3 in which the switch assembly I I is mounted. Anintermediate section I 4 and a bottom section I5 of said housing definethe chamber inwhich the bellows motor I3 is supported. The upper memberand the intermediate member are secured together preferably by means offour bolts designated I 6 which extend through suitable flanges I'I.vThe lower member I3 is secured to the intermediate member by means of athreaded connection shown at I8.

The switch assembly, herein shown, comprises a base I9 on which a,switch arm 20 and a fixed contact 2| are cooperatively mounted.Preferably, the base I9 of the switch assembly is se` cured to the innerupper surface of the housing by means of four screws 22. Spacing sleeves23 of insulating material surround the said screws and hold the base I Sin a, predetermined spaced position relative to said inside uppersurface of the housing. 'I'he switch arm 20 is xed to a boss 24 formedon the base so that its contact 25 on the movable end of the arm willassume a. predetermined position relative to the iixed contact 2 I. Theswitch arm 20 may be and preferably is of the special constructiondescribed and claimed in the' copending application of William R..Peterson and Allen G.- Ford, Serial No. 464,580, filed November 5, 1942.inasmuch as the switch arm per se is claimed in said copendingapplication, it will be sufficient for a full understanding of theinvention to describe the said switch arm 2U as comprising a springmetal plate, the center portion of which is severed from the main bodyandbent outwardly at an angle thereto to provide an operating lever 26.The main body of the switch arm is formed intermediate its ends 45 withU-shaped bends 21, whereby the switch arm is made yieldable in thedirection of its length as '-well as flexible transversely. Avrigidrocker member 28 is interposed between the outer end oi the operatinglever 21 and the contact end of 50 the switch arm 20. Consequently, whenthe operating lever 26 is depressed from the position indicated in Fig.2 to a, position below the center of arm 2l, the resiliency of the armcauses it to snap upwardly against the iixed contact 2I and 55 therebycloses an electrical circuit through the lead wires 29 and 30.

With the switch assembly mounted as shown in Figs. 1 and 2, the switcharm 2li is caused to move into engagement with the iixed contact so 2|by application of pressure downwardly against the operating lever 28.This pressure is provided by means of a spring pressed plunger Il, theupper end 32 of which is slidably fitted in a spring Achamber 33 formedin the upper portion or the housing. The lower portion 34 of the plungeris reduced in diameter and extends through a central opening 35 in thebase i9 so as to support and guide the plunger in its reciprocatingmovements. The plunger, it will be seen, bears upon the operating lever21 and is pressed downwardly by means of a helical spring 38 interposedbetween the upper end of the `plunger and an adjusting screw 31. Whenthis spring pressure is relieved, the resiliency of the switch arm 20will cause the arm 20 to snap across its dead center position, but inthe opposite direction. The said spring pressure is relieved by means ofa pressure motor, preferably a bellows 39 closed at its lower end andhaving its outwardly flanged upper end 40 clamped between the lower andintermediate sections i4 and i of the housing. This manner of attachmentprovides a pressure chamber 4i between the outer face of the bellows andthe inner face of the lower section i3 of the housing. A push rod 42 isfixed to the bottom wall of the bellows and is provided at its upper endwith a cup 43 which receives the lower end 34 of the operating plungerSi. It will be seen, therefore, that upon the development of pressure inthe pressure chamber 4i, the bellows will be caused to contract andthereby force the operating plunger 3l upwardly against the compressionof the helical spring 36. This upward movement of the plunger removesthe pressure from the switch operating lever 2E and thereby permits theswitch arm to snap away from said xed contact 2 i.

In order to protect the switch contacts from the collection of dust andat the same time make the switch suitable for use in situations wherethe likelihood of an open spark would be objectionable, a fiexiblediaphragm 44 is clamped between the upper and intermediate sections ofthe housing and engages in a` groove formed in the push rod 42 so as toprovide a sealed chamber in which the switch assembly is mounted.

In Figs. l, 2 and 3 the pressure chamber 4l communicates with a tube -45containing a volatile fluid which upon a rise of temperature willvolatilize or otherwise expand so as to increase the pressure in chamber4|, thereby causing the bellows 39 to contract and thereby effectmovement of the switch arm 20 in the direction previously described.

The particular pressure required to operate the switch may be obtainedby appropriate adjustment of screw 31. A bonnet cap 46 ts over the upperend of the screw and serves as a lock nut to hold the screw 31 in anydesired position.

In Figs. 4 and 5 the switch assembly designated il is mounted in thehousing in an inverted position so that the switch arm designated 20will be normally held spaced from the fixed contact designated 2P.

With the arrangement of parts, as shown in Figs. 4 and 5, the pressureof spring 36a functions to move the switch arm 2lia to its normally openposition. The development of pressure in the pressure chamber 4l causesthe bellows 39 to contract and thereby presses the cup shaped portion43a of push rod 42a against the switch operating lever 21B. When thislever is pressed upwardly beyond the center of switch arm 20, the rigidrocking member 28* assumes an angular 4 position to snap the contact end25* into engagement with the fixed contact 2 I In the embodimentillustrated in Fig. 6, the pressure actuated switch is designed for usein the special situation illustrated, to-wit as a control for theelectric heater circuit of a coffee maker. In this embodiment thereference numeral 41 designates a supporting structure, 4l a heatresistant disk, and 49 and 50 designate ring shaped cases in whichheating wires (not shown) are suspended in a heat-resisting filler. Theheat generated in the heating wires is conducted through the casings 49and 50, to the container 5i in which the coffee is being made. The heatfrom the heating elements 49 and ll is transmitted through a plate 52 tothe outer face of a casing 53 defining the outer wall of the pressuremotor chamber 54. The pressure motor in the present embodiment comprisesa bellows 55 of a construction similar to that illustrated -in thepreceding embodiments arranged within the casing 53 so as to providesaid chamber 54. An operating rod 56 extends downwardly from the closedupper end of the bellows, and carries at its lower end an adjusting nut51. The adjusting nut engages a sleeve member `53 guided in openings 59and 60 in the base members Si,l 62. The said sleeve member 5B includesan enlarged portion 63 which engages the operating lever 64 of theswitch arm 65. The switch arm 65 of the present embodiment may be, andpreferably is, identical with the switch arms employed in the precedingfigures. A helical spring 66 is interposed between a screw plug l1 andthe upper end of the bellows. The adjustment of said nut 51 determinesthe pressure required to operate the switch arm in one direction andconsequently determines the temperature at which the switch is set tooperate.

While the invention is illustrated herein in connection with thespecific embodiments shown, and in one specihc situation, it will beunderstood that the invention is not to be restricted to the specificembodiments shown or to the specific use illustrated except in so far asspecific limitations may appear in the appended claims.

Iclaim:

l. A pressure actuated switch, for controlling an electric circuitcomprising, in combination, a switch assembly formed with an openingtherethrough, a temperature responsive motor positioned at one side ofsaid switch assembly for moving the switch arm thereof in one direction,resilient means positioned at the othel side of said switch assembly, amovable element associated with said resilient means extending throughsaid opening in said switch assembly and engaging the switch armoperating member of the motor for moving the motor in the oppositedirection, adjustable means associated with said resilient means to varythe pressure exerted thereby and thereby determine the temperature atwhich the switch arm will function, means for mounting the switchassembly relative to said motor and said resilient means, a housing inwhich said switch assembly and said temperature responsive motor areenclosed, and a flexible diaphragm extending across said housingintermediate said motor and said switch assembly, whereby the saidswitch assembly is contained in a dust-proof compartment.

2. A pressure actuated switch comprising, in combination, a casing, aswitch means mounted in said casing for opening and closing an electriccircuit, a temperature responsive motor in said casing for actuating theswitch; the said casing including a plurality of separable sections andthe motor comprising a bellows closed at its lower end and having itsother end clamped between two adjacent sections of the casing so as tofacilitate the assembly of the structure and'to provide an expansionchamber between the bellows and one of said sections of the casing forcontaining a thermosensitive liquid adapted to vary the pressure in saidexpansion chamber in relation to temperature changes, means comprising apush rod connected to the closed lower end of the bellows for detachablyconnecting the said motor with a movable element of said switch, and aflexible diaphragm between two adjacent sections of the casing andconnected with said push rod so as to provide a dust-proof chamber forsaid switch.

3. A pressure actuated switch' comprising, in combination, a casing, a.switch means mounted inV said casing for opening and closing an electriccircuit, a temperature responsive motor in said casing for actuating theswitch; the said casing including a plurality of separable sections toprovide ready access to the upper and lower portions of the casing andthe motor comprising a bellows closed at its lower end and having itsother end clamped between two adjacent sections of the casing so as tofacilitate the assembly of the structure and to provide an expansionchamber between the bellows and one of said sections of the casing forcontaining a thermosensitive liquid adapted to vary the pressure in saidexpansion chamber in relation to temperature changes, means comprising apush rod connected to the closed lower end of the bellows for detachablyconnecting the said motor with a movable element of said switch, aflexible diaphragm between two adjacent sections of the casing andconnected with said push rod so as to provide a dust-proof chamber forsaid switch, and a tu# bular extension for said expansion chamberadapted to contain a portion of thermosensitive liquid, whereby the saidmotor is made responsive to temperature changes at a location remotefrom the motor.

4. A pressure actuated switch comprising, in combination, a casing, aswitch means mounted in said casing for opening and closing an electriccircuit, a temperature responsive motor in said casing for actuating theswitch; the said casing including a plurality of separable sections tofacilitate assembly of the structure and the motor comprising a bellowsclosed at its lower end and having its other end clamped between twoadthermosensitive liquid adapted to vary the pres- 6 jacent sections ofthe casing so as to provide an expansion chamber between the bellows andone of said sections of the casing for containing a sure in saidexpansion chamber in relation to temperature changes, means comprising apush rod connected to the closed lower end of the bellows for detachablyconnecting the said motor with a movable element of said switch, ailexible diaphragm between two adjacent sections of the casing andconnected with said push rod so as to provide a dust-proof chamber forsaid switch, and means associated with said expansion chamber forconducting heat thereto from a location remote from said chamber.

5. A pressure actuated switch comprising, in combination, a casing, aswitch means mounted in said casing for opening and closing an electriccircuit, a temperature responsive motor in said casing for actuating theswitch; the said casing including a plurality of separable sections andthe motor comprising a, bellows closed at its lower end and having itsother end clamped between two adjacent sections of the casing so as toprovide an expansion chamber between the bellows and one of saidsections of the casing for containing a thermosensitive liquid adaptedto vary the pressure in said expansion chamber in relation totemperature changes, means comprising a push rod connected to the closedlower end of the bellows for detachably connecting the said motor with amovable element of said switch, a Vilexible diaphragm between twoadjacent sections of the casing and connected with said push rod so asto 'provide a dust-proof chamber for said switch,

means associated with said expansion chamber for conducting heat theretofrom a location remote from said chamber, and a metallic heat conductorextending from the pressure chamber casing to a heated zone remote fromsaid motor, whereby the motor is made responsive to the temperature ofsaid heated zone.

WILLIAM R. PETERSON.

REFERENCES CITED The following references are of record in the ille ofthis patent:

UNITED STATES PATENTS Number Name Date 1,985,337 Bondurant Dec. 26, 19342,150,203 Bondurant Mar. 14, 1939 2,102,176 Dillman Dec. 14, 19371,908,088 Warner May 9, 1933

